Are comorbidities associated with long-term survival of lung cancer? A population-based cohort study from French cancer registries.

Background: Survival rates of lung cancer remains poor and the impact of comorbidities on the prognosis is discussed. The objective of this study was to assess if the Charlson Comorbidity Index (CCI) was associated with 8-year survival rates by histological type.
Methods: A cohort study was conducted using randomly selected cases from 10 French cancer registries. Net survival rates were computed using the Pohar-Perme estimator of the net cumulative rate. Three Cox models were independently built for adenocarcinomas, squamous cell and small cell cancers to estimate prognostic factors including CCI grade.
Results: A total of 646 adenocarcinomas, 524 squamous cell and 233 small cell cancers were included in the analysis. The net 8-year survival rate ranged from 12.6% (95% CI: 9.8-15.4%) for adenocarcinomas and 13.4% (95% CI: 10.1-16.7%) for squamous cell carcinomas, to 3.7% (95% CI: 1.1-6.3%) for small cell cancers. Observed and net survival rates decreased for CCI grades ≥3 for all histological group considered. After adjustment for sex, age group, stage and diagnostic mode, CCI grades 1 (HR = 1.6 [95% CI: 1.1-2.3]), 2 (HR = 1.7 [95% CI: 1.1-2.7]) and ≥ 3 (HR = 2.7 [95% CI: 1.7-4.4]) were associated with lower survival rates only for small cell cancers.
Conclusion: After adjustment for age, sex, stage and diagnostic mode, the presence of comorbidity based on CCI grades 1-2 and ≥ 3 was associated with lower survival rates for small cell cancers whereas no differences were observed for adenocarcinomas and squamous cell cancers.